Compound bows with modified cams
A compound bow comprising a handle portion having a first limb and a second limb extending outwardly therefrom, a wide body cam assembly pivotally coupled to the first limb near an outer end thereof, and a dual wheel assembly pivotally coupled to the second limb near an outer end thereof. The wide body cam assembly comprises a main sheave and a collector sheave located on opposite sides of a cable sheave. The main sheave is spaced apart from the cable sheave by a first distance sufficient to permit arrows to be fired from the bow free from interference by a cable without the use of a cable guard. The dual wheel assembly comprises a feed out sheave and a take in sheave separated by a second distance which is larger than the first distance. The feed out sheave is positioned substantially within a plane defined by the main sheave.
This invention relates generally to the field of compound archery bows. In particular, certain embodiments of the invention relate to single cam type compound archery bows.
BACKGROUNDCompound archery bows typically have a bowstring, on which an arrow may be nocked, along with one or more portions of cable other than the bowstring extending between the limbs of the bow. Such cable portions, sometimes referred to as “power cables”, are generally located at least partly within or close to an operating plane of the bowstring. The power cables thus interfere with shooting arrows.
In order to provide adequate room for the arrow, it is conventional practice to mount a cable guard on the bow to engage the central portions of the power cables and to displace them laterally a sufficient distance to one side of the operating plane of the bowstring to avoid interference with an arrow. One drawback associated with conventional cable guards is that, in displacing the center of a power cable laterally from its straight line position, they introduce a lateral component to the force exerted by the power cable against the limbs. This lateral torque not only decreases the accuracy of arrow flight, but also causes twisting of the limbs, cams, wheels and/or handle, and thereby contributes adversely to shortening their useful life. Conventional cable guards also cause the power cables to feed on and off of the cams and wheels at an angle. This may sometimes lead to the power cables becoming dislodged from the cams and/or wheels.
There exist a number of prior art systems, other than cable guards, for preventing the power cables from interfering with the shooting of arrows from compound bows. Examples include U.S. Pat. No. 5,623,915 to Kulacek and No. 6,729,320 to Terry, and U.S. patent application Ser. No. 11/968,459 to Evans.
The inventor has determined a need for further systems which do not require cable guards to prevent power cables from interfering with the flight of arrows.
SUMMARYOne aspect of the invention provides a compound bow comprising a handle portion having a first limb and a second limb extending outwardly therefrom, a wide body cam assembly pivotally coupled to the first limb near an outer end thereof, and a dual wheel assembly pivotally coupled to the second limb near an outer end thereof. The wide body cam assembly comprises a main sheave and a collector sheave located on opposite sides of a cable sheave. The main sheave is spaced apart from the cable sheave by a first distance sufficient to permit arrows knocked on a bowstring portion extending between the main sheave and the feed out sheave to be fired from the bow free from interference by a cable extending within a plane defined by the cable sheave without the use of a cable guard. The dual wheel assembly comprises a feed out sheave and a take in sheave separated by a second distance which is larger than the first distance. The feed out sheave is positioned substantially within a plane defined by the main sheave.
Another aspect of the invention provides a wide body cam assembly for a compound bow. The wide body cam assembly comprises a main sheave and a collector sheave located on opposite sides of a cable sheave. The main sheave is spaced apart from the cable sheave by a distance of at least a radius of an arrow and its fletching.
Another aspect of the invention provides a dual wheel assembly for a compound bow. The dual wheel assembly comprises a feed out sheave and a take in sheave separated by a spacer. The spacer is configured such that the feed out sheave and the take in sheave are separated by a distance of at least twice a radius of an arrow and its fletching.
Another aspect of the invention provides a cam assembly for a compound bow. The cam assembly comprises a main sheave and a collector sheave located on opposite sides of a cable sheave. A pair of protrusions extend laterally outwardly from the main sheave and the collector sheave. The protrusions are adapted to be rotatably received in a pair of sockets defined in an end portion of a limb of the compound bow, such that no axle is required for coupling the cam assembly to the bow.
In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the drawings and by study of the following detailed descriptions.
In drawings which illustrate non-limiting example embodiments of the invention:
Throughout the following description specific details are set forth in order to provide a more thorough understanding to persons skilled in the art. However, well known elements may not have been shown or described in detail to avoid unnecessarily obscuring the disclosure. Accordingly, the description and drawings are to be regarded in an illustrative, rather than a restrictive, sense.
Cam assembly 30 comprises three parallel sheaves (not shown in
Other differences between bow 100 and various types of prior art bows may also exist. For example, an arrow rest portion 21 on handle portion 20 may be somewhat wider on bow 100 than on some prior art bows to accommodate the modified nocking position of bow 100, as discussed below.
As one skilled in the art will appreciate, dual wheel assembly 110 and wide body cam assembly 130, or variations thereof, could be used with a variety of different types of compound bow. For example,
As shown in
As shown in
Bowstring portion 50B may be wound around the back side of feed out sheave 112 and anchored thereto, and bowstring portion 50A may be wound around the front side of take in sheave 114 and anchored thereto. As shown in
As dual wheel assembly 110 rotates when bow 100 is being drawn, bowstring portion 50A winds onto take in sheave 114 and bowstring portion 50B winds off of feed out sheave 112, such that when bow 100 is in a drawn position (see
As shown in
Bowstring portions 50B and 50A may be wound around the back sides of main and collector sheaves 132 and 134, respectively, and anchored thereto. Cable 40 may be wound around the front side of cable sheave 136 and anchored thereto. When the bow is in its undrawn position (see
As shown in
Wheel assembly 110 and cam assembly 130 may be configured such that feed out sheave 112 and main sheave 132 are substantially coplanar. Feed out sheave 112 and main sheave 132 define an operating plane for bowstring portion 50B. Cable sheave 136 of cam assembly 130 defines an operating plane for cable 40 which may be parallel to the operating plane for bowstring portion 50B and separated therefrom by distance D1. The spacing between main sheave 132 and cable sheave 136 ensures that cable 40 remains far enough away from the operating plane of bowstring portion 50B to avoid interfering with the shooting of arrows. The need for a cable guard is thus avoided.
Distance D1 is selected such that arrows nocked on bowstring portion 50B may be fired from bow 100 free from interference by cable 40, without requiring a cable guard. For example, as shown in
The operating plane of bowstring portion 50B may thus be offset from the lateral center of bow 100. As noted above, bow 100 preferably comprises an arrow rest portion 21 which is large enough to extend through the operating plane of bowstring portion 50B to support an arrow nocked thereon.
Take in sheave 114 and collector sheave 134 may also be substantially coplanar. The operating plane of bowstring portion 50A may thus be separated from cable sheave 136 by distance D2.
In some embodiments, distance D2 is selected to be equal to distance D1, such that main sheave 132 and collector sheave 134 are equally separated from cable sheave 136 on either side thereof. Similarly, feed out sheave 112 and take in sheave 114 may be symmetrically positioned on wheel assembly 110. Such a configuration may balance the forces on wheel assembly 110 and cam assembly 130 and thus minimize twisting of limbs 22 and 24. For example, in embodiments where bowstring portions 50A and 50B are part of a continuous bowstring 50, bowstring 50 tends to “self center”, such that the forces exerted by bowstring portions 50A and 50B tend to be substantially equal to each other.
In other embodiments, D1 and D2 may not be equal. Such embodiments may be suitable, for example, if the forces exerted by bowstring portions 50A and 50B are not equal, due to differences in the compositions and/or lengths of bowstring portions 50A and 50B or other factors. In such embodiments, D1 and D2 may be selected based on the ratio of the forces exerted by bowstring portions 50A and 50B to minimize twisting of limbs 22 and 24.
Wheel assembly 110 and cam assembly 130 may also be configured to ensure that nock 60 moves linearly, or at least substantially linearly, as bow 100 is fired (sometimes referred to as a “flat nock”). For example, a flat nock may be achieved by selecting appropriate peripheral profiles for the sheaves of the cam assembly, as described in U.S. Pat. No. 5,782,229.
Cam assemblies 130A, 130B and 130C (collectively cam assemblies 130) are all the same except for the configuration of cable sheaves 136A, 136B and 136C. As discussed in U.S. Pat. No. 5,782,229, the draw force curve of a compound bow may be altered by changing the configuration of the cable sheave. In some embodiments, removable modules (not shown) similar to those described in the above noted U.S. Pat. No. 5,782,229 may be provided for altering the profile of cable sheave 136 and producing varying draw force curves. In some embodiments, cable sheave 136, or a portion thereof, may be rotatable with respect to cam assembly 130 in a manner similar to that described in U.S. Pat. Nos. 4,686,955 and 4,774,927 to Larson, which are hereby incorporated by reference herein, in order to produce varying draw force curves.
The range of variation of the cable sheave disclosed in U.S. Pat. No. 5,782,229 and other prior art compound bows is limited by the presence of an axle through the cam assembly. By providing protrusions 142 instead of an axle, cam assemblies according to certain embodiments of the invention may be provided with a wider range of cable sheave profiles. For example, cable sheaves of cam assemblies of some embodiments may be configured to be very close to or along axis 141 at some points around the peripheral profile thereof (as illustrated by cable sheave 136B of
Dual wheel assembly 110 may also be rotatably mounted to limb 22 without the use of an axle. As shown in
With reference to
In some embodiments, cut out portions 118 of sheaves 112, 114 are angularly offset from each other such that the radius of the peripheral profile of each sheave 112, 114 remains relatively constant at the point at which each bowstring portion 50B, 50A contacts the respective sheave 112, 114 throughout the range of motion of dual wheel assembly 110. For example, in some embodiments, cut out portions 118 may be angularly offset from each other by an angle ranging from 60 to 180 degrees. The angular extent of the arc portion of the peripheral profile of each sheave 112, 114 may, for example, range from about 220 to 300 degrees in some embodiments. In some embodiments, the angular extent of the arc portion of the peripheral profile of each sheave 112, 114 may, for example, be selected based on the size and shape of main sheave 132.
In the illustrated example, each sheave 112, 114 has an inwardly angled portion 112A, 114A, respectively, extending into cut out portion 118. An anchor post 113, 115 is located at or near the end of each respective inwardly angled portion 112A, 114A, for anchoring the respective bowstring portion 50B, 50A. As noted above, bowstring 50 may be continuous or may comprise separate parts. In embodiments where bowstring 50 is continuous, bowstring 50 may comprise an intermediate portion 50C extending between take in sheave 114 and feed out sheave 112 around or across spacer 116. In such embodiments, bowstring 50 may wrap around each of posts 113 and 115 to prevent bowstring 50 from slipping relative to wheel assembly 110, such that intermediate portion 50C does not move with respect to wheel assembly 110 as the bow is fired. Also, spacer 116 may optionally define a groove (not shown) therein for receiving intermediate portion 50C of bowstring 50. In embodiments where bowstring 50 is continuous, bowstring portion 50A may be anchored to collector sheave 134, extend upward to and partially around take in sheave 114, wrap around post 115, continue across and around spacer 116 as intermediate portion 50C, wrap around post 113, continue around feed out sheave 112 as bowstring portion 50B, and extend down to be anchored to main sheave 132. In embodiments where bowstring 50 is in two parts, intermediate portion 50C may be omitted, and bowstring portion 50A may terminate at post 115 and bowstring portion 50B may terminate at post 113, for example.
Dual wheel assembly 110 and wide body cam assembly 130 may be constructed using a variety of techniques. In some embodiments dual wheel assembly 110 and wide body cam assembly 130 may each be machined from a block of metal such as, for example, aluminum. In other embodiments, dual wheel assembly 110 and wide body cam assembly 130 may be formed by injection molding using a high strength plastic or other polymeric material. In still other embodiments, the some or all of the various sheaves and spacers of dual wheel assembly 110 and wide body cam assembly 130 may be individually formed (either through machining or injection molding), and the individually formed parts may then be bolted or otherwise securely fastened together.
While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and sub-combinations thereof. For example:
-
- In the illustrated embodiments, the dual wheel assembly is mounted on the “upper” limb of the bow (with respect to the orientation of the bow's handle) and the wide body cam assembly is mounted on the lower limb of the bow. The locations of the dual wheel assembly and the wide body cam assembly could be exchanged in other embodiments.
- The bodies of the sheaves of the wheel assembly and/or the cam assembly may have a number of openings therethrough, as shown in the illustrated embodiments, to reduce the weights thereof. The bodies of the sheaves could be generally solid in other embodiments.
It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations as are within their true spirit and scope.
Claims
1. A single cam compound bow comprising:
- a handle portion having a first limb and a second limb extending outwardly therefrom;
- a wide body cam assembly pivotally coupled to the first limb near an outer end thereof, the wide body cam assembly comprising a main sheave and a collector sheave located on opposite sides of a cable sheave, the main sheave spaced apart from the cable sheave by a first distance;
- a dual wheel assembly pivotally coupled to the second limb near an outer end thereof, the dual wheel assembly comprising a feed out sheave and a take in sheave held in fixed relation to one another to rotate in unison and separated by a second distance which is larger than the first distance, the feed out sheave positioned substantially within a plane defined by the main sheave;
- a first bowstring portion having a nock point thereon for nocking an arrow, the first bowstring portion extending from the main sheave of the wide body cam assembly to the feed out sheave of the dual wheel assembly and a second bowstring portion extending from the collector sheave of the wide body cam assembly to the take in sheave of the dual wheel assembly; and,
- a cable having a first end coupled to the cable sheave of the wide body cam assembly and a second end comprising a split portion coupled to a pair of attachment points on or near the outer end of the second limb on either side of the dual wheel assembly
- wherein the first distance is sufficient to permit arrows knocked on the first bowstring portion extending between the main sheave and the feed out sheave to be fired from the bow free from interference by a cable extending within a plane defined by the cable sheave without the use of a cable guard.
2. A single cam compound bow according to claim 1 wherein the take in sheave is positioned substantially within a plane defined by the collector sheave.
3. A single cam compound bow according to claim 2 wherein the collector sheave is spaced apart from the cable sheave by the first distance.
4. A single cam compound bow according to claim 1 wherein the first distance is at least 0.5 times a radius of a three-vaned arrow and its fletching.
5. A single cam compound bow according to claim 1 wherein the first distance is at least 0.707 times a radius of a four-vaned arrow and its fletching.
6. A single cam compound bow according to claim 1 wherein the first distance is at least a radius of an arrow and its fletching.
7. A single cam compound bow according to claim 1 wherein the first distance is at least ⅝″.
8. A single cam compound bow according to claim 1 wherein the feed out sheave and the take in sheave are substantially parallel to one another, and the main sheave, the collector sheave and the cable sheave are substantially parallel to one another.
9. A single cam compound bow according to claim 1 wherein the outer end of the first limb comprises a pair of sockets defined therein, and wherein the wide body cam assembly comprises a pair of protrusions extending laterally outwardly therefrom, the protrusions adapted to be rotatably received in the pair of sockets defined in the outer end of the first limb.
10. A single cam compound bow according to claim 9 wherein the sockets comprise bearings or bushings.
11. A single cam compound bow according to claim 10 wherein an axis of rotation of the wide body cam assembly lies along or outside of a peripheral profile of the cable sheave.
12. A single cam compound bow according to claim 1 wherein the outer end of the second limb comprises a pair of sockets defined therein, and wherein the dual wheel assembly comprises a pair of protrusions extending laterally outwardly therefrom, the protrusions adapted to be rotatably received in the pair of sockets defined in the outer end of the second limb, the sockets comprising bearings or bushings.
13. A single cam compound bow according to claim 1 wherein the wide body cam assembly comprises a first spacer between the main sheave and the cable sheave and a second spacer between the collector sheave and the cable sheave.
14. A single cam compound bow according to claim 13 wherein the dual wheel assembly comprises a third spacer between the feed out sheave and the take in sheave.
15. A single cam compound bow according to claim 1 wherein the first and second bowstring portions comprise portions of a single continuous bowstring, the first and second bowstring portions connected by an intermediate bowstring portion extending between the take in sheave and the feed out sheave of the dual wheel assembly.
16. A single cam compound bow according to claim 1 wherein the first and second bowstring portions comprise separate elements.
17. A single cam compound bow according to claim 16 wherein the collector sheave is spaced apart from the cable sheave by a third distance having a ratio with the first distance based at least in part on a ratio of forces exerted by the first and second bowstring portions so as to minimize twisting of the limbs.
18. A single cam compound bow according to claim 1 wherein the main sheave, the collector sheave and the cable sheave of the wide body cam assembly have peripheral profiles configured such that the nock point moves substantially linearly as the bow is fired.
19. A single cam compound bow according to claim 1 wherein the feed out sheave and the take in sheave of the dual wheel assembly each comprise a peripheral profile having a cut out portion and an arc portion.
20. A single cam compound bow according to claim 19 wherein the cut out portions of the peripheral profiles of the feed out sheave and the take in sheave are angularly offset from each other.
21. A single cam compound bow according to claim 20 wherein the arc portions of the peripheral profiles of the feed out sheave and the take in sheave range in angular extent from 220 to 300 degrees.
22. A single cam compound bow according to claim 21 comprising an anchor post located along an inwardly angled side of each of the cut out portions of the peripheral profiles of the feed out sheave and the take in sheave.
23. A single cam compound bow according to claim 21 comprising a spacer between the feed out sheave and the take in sheave and an anchor post located on the spacer.
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Type: Grant
Filed: Apr 28, 2009
Date of Patent: Oct 4, 2016
Patent Publication Number: 20100269808
Inventor: John D. Evans (Calgary)
Primary Examiner: Melba Bumgarner
Assistant Examiner: Amir Klayman
Application Number: 12/431,435
International Classification: F41B 5/10 (20060101); F41B 5/14 (20060101);